The present invention relates to photographic photosensitive solution manufacturing method and apparatus for practicing such a method. More particularly, the invention relates to a method for mixing Ag.sup.+ and X.sup.- solutions to produce crystals of silver halide emulsion in a photographic photosensitive solution manufacturing process, and to an apparatus for practicing such a method.
Examples of a conventional method for adding Ag.sup.+ and X.sup.- solutions to produce crystal of silver halide emulsion in a photographic photosensitive solution manufacturing process and a conventional apparatus for practicing such a method include a method and apparatus in which the addition is controlled by means of a pump (see, for instance, U.S. Pat. Nos. 4,147,551 and 4,251,627) and a method and apparatus in which the addition is controlled by means of a control valve (see, for instance, U.S. Pat. Nos. 3,692,283, 3,897,935, 3,999,048, 4,026,668 and 4,031,912).
However, the method in which the addition is controlled by means of a pump suffers from the following difficulties:
(1) In a batch-type process, after addition, some expensive Ag.sup.+ solution must be left in the tank and pipes in order to prevent idling of the pump. That is, all the prepared solution cannot be used.
(2) When Ag.sup.+ solution is supplied with the pump, Ag will deposit, for instance, on the sealed parts of the pump, thus obstructing the operation of the same.
(3) The pulsation of the pump adversely affects the formation of particles. Therefore, the resultant emulsion particles tend to greatly vary in size and shape.
(4) In the case where various different solutions are to be manufactured on a small scale, requisite cleaning of the apparatus takes a significantly long time.
On the other hand, the method and apparatus in which addition is controlled by means of a control valve is disadvantageous in the following points:
(1) The diaphragm control valve generally used in such a method and apparatus generally has a low flow control accuracy, which causes the resultant emulsion particles to vary widely in size and shape.
(2) To manufacture a variety of different photosensitive solutions, the flow rate must be changed. However, since the relation of the flow rate to the degree of valve opening is not linear, it is difficult to maintain ideal control conditions.
(3) Because the diaphragm control valve is particularly low in flow control accuracy near the fully opened and fully closed positions, the flow control range is limited. Therefore, in order to be able to manufacture a variety of different photosensitive solutions, it is necessary to provide a plurality of diaphragm valves of different sizes. This adversely affects the overall system design, space utilization, and load of control.